The coating of flexible substrates such as ultra-thin glass or web with functional layers is highly efficient thanks to the use of roll-to-roll (R2R) technologies. Crucial for plant operators and ultimately for the price is the coating thickness homogeneity and thus also the electrical properties of the applied coatings for a high and above all constant yield without rejects. Until now, the electrical properties of the coating could only be determined and analyzed at defined measuring points. Within the joint project KODOS – Fabricated Thin Glass Composite for Optoelectronic Systems (funding reference 13N14607), funded by the German Federal Ministry of Education and Research, an integrable solution for in-line process monitoring and mapping of process parameters was developed with the project partner SURAGUS GmbH at Fraunhofer FEP in Dresden. This unique solution enables in-situ 2D monitoring for the first time using traversable eddy current measuring heads and thus more detailed process optimization during coating.
Utilizing roll-to-roll (R2R) manufacturing processes is emphasized for their ability to produce flexible devices in large quantities, with a keen focus on optimizing yield to reduce the cost per square meter of flexible materials. Maintaining high yield and continually improving it is vital for cost-effectiveness. Identifying and understanding defects in coatings and their causes during processing is foundational for process optimization. Traditionally, post-processing analysis was used to identify defects, but the introduction of inline monitoring allows real-time analysis during the coating process, minimizing reject rates by swiftly detecting inhomogeneities and process fluctuations.
Fraunhofer FEP, a leading research institute in R2R coatings, collaborates with project partners like SURAGUS GmbH to advance coating technologies for electrodes and OLEDs. They’ve developed a self-sufficient traverse installation to characterize essential electrical properties of material composites close to the process. This innovative solution integrates movable eddy current sensors, enabling non-contact high-frequency eddy current testing for precise monitoring of coating quality and process stability. The traverse system offers two-dimensional sensor mobility, allowing in-situ monitoring of sheet resistivity and coating thickness fluctuations during the R2R process, a significant advancement from previous one-dimensional fixed-position sensor capabilities. This technological leap enables real-time adjustments and enhances process control during coating, ultimately contributing to improved manufacturing efficiency and potential applications across various industries. The project partners remain open to further developments and applications, showcasing the adaptability and potential of this unique traverse solution with two-dimensional movable sensors in existing R2R plant technology.
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